Retaining Wall Rocks: How to Choose and Build with Rockery Stone

A well-built rock retaining wall is one of the most durable and beautiful landscape features you can add to a Kitsap County property. Done right, it lasts generations with zero maintenance. Done wrong, it fails within a few years — usually because of poor drainage or the wrong materials.

This guide covers everything: stone types, wall construction basics, drainage requirements, and how to order the right materials.

Types of Retaining Wall Rock

Rockery Stone (Fieldstone)

Large, angular granite or basalt boulders, typically 200-1,000+ lbs each. The Pacific Northwest standard for retaining walls. These are the classic moss-covered stacked rock walls you see throughout Kitsap and Pierce Counties. Extremely durable — properly built rockery walls have been standing for 50-100+ years in our region.

Best for: Walls over 18 inches high, slopes with significant weight, long-term permanence.

Smaller Flat Rock (Dry-Stack)

Flat, roughly rectangular stones that stack without mortar. Requires skilled placement but creates beautiful, naturally draining walls. Popular for garden borders, raised bed walls, and decorative terrace walls under 3 feet.

Boulders (Accent/Feature)

Single large boulders used as focal points or to anchor wall ends. Available in granite, basalt, and decorative varieties.

Concrete Block (Not Our Territory)

We carry natural stone. Concrete retaining block (Allan Block, Versa-Lok) is available at big-box stores but lacks the permanence and natural look of rockery.

Wall Construction Basics

Batter: The Critical Concept

A rockery wall should lean slightly into the slope — about 1 inch back for every foot of height. This "batter" uses gravity to keep the wall in place. A vertical wall has no batter and relies entirely on stone weight — it's weaker and more prone to failure.

Rule of Thumb for DIY Height Limits

• Walls under 3 feet: DIY-friendly with proper drainage and batter
• Walls 3-4 feet: DIY possible with careful technique and significant stone size
• Walls over 4 feet: Professional recommended; engineering may be required

Foundation Matters

The base course (bottom row) should be your largest stones, set below grade. For every foot of wall height, bury the base stones 6-8 inches underground. A 3-foot wall needs base stones set 18-24 inches below ground level.

Drainage: The Make-or-Break Element

More retaining walls fail from poor drainage than from insufficient stone weight. When water saturates the soil behind a wall, hydrostatic pressure builds — eventually enough to push even large stones out of alignment.

The Essential Drainage Layer

Every retaining wall needs:

1. Drainage rock backfill: 12-18 inches of clean 3/4" crushed rock directly behind the wall. Never clay, never topsoil.
2. Drain pipe: Perforated 4" pipe at the base of the wall, set in the drainage rock, running to daylight at each end.
3. Filter fabric: Separating the drainage rock from the retained soil to prevent migration.

Order our clean crushed rock for retaining wall drainage — delivered by the yard directly to your project site.

How Much Drainage Rock Do You Need?

For a wall 3 feet high × 50 feet long with 18" drainage zone:

1.5 ft wide × 3 ft deep × 50 ft long ÷ 27 = 8.3 cubic yards of drain rock

Use our cubic yard calculator for your specific dimensions.

Step-by-Step: Building a Basic Rockery Wall

Step 1: Lay Out and Excavate

• Mark the wall line with stakes and string
• Excavate a trench for your base stones — depth = 1/3 of wall height minimum
• Excavate the drainage zone behind where the wall will sit

Step 2: Set the Base Course

• Place your largest stones first, set into the trench
• Ensure they're stable and level across the top (shimming with smaller stones is fine)
• Begin setting the batter angle — lean stones slightly into the slope

Step 3: Build Up in Courses

• Each course of stone should overlap the joints of the course below (like brickwork)
• Select stones that fit together snugly; use smaller "chinking" stones to fill gaps
• Continue setting batter as you go up — roughly 1 inch setback per foot of height

Step 4: Install Drainage As You Build

• As you raise each course, backfill behind with clean crushed rock (not topsoil)
• Set the perforated drain pipe at base level before backfilling more than 6 inches
• Wrap pipe in filter fabric at the inlet/outlet points

Step 5: Cap and Finish

• Top course: largest, flattest stones that won't shift
• Backfill remaining drainage zone with rock, then a 4-inch topsoil cap
• Plant or mulch the retained area above the wall

Ordering Rockery Stone in Gig Harbor and Kitsap County

Harbor Soils delivers rockery stone, boulders, and drainage rock to project sites throughout Gig Harbor, Port Orchard, Purdy, Artondale, Fox Island, and surrounding areas.

For walls, we'll help you estimate the tonnage needed based on your wall dimensions. Rockery is sold by the ton; drainage rock is sold by the cubic yard.

Frequently Asked Questions

How much rockery stone do I need?

A rough rule: 1 ton of rockery stone covers approximately 20-25 square feet of wall face (at typical 12-18" average stone depth). A wall 30 feet long × 3 feet high = 90 square feet face → approximately 4-5 tons of rockery stone.

Can I build a retaining wall without drainage?

In sandy, free-draining soil, possibly. In western Washington's clay soils — absolutely not. Hydrostatic pressure will eventually push any wall that doesn't have proper drainage. Even small walls benefit from drainage rock behind them.

What is the difference between a dry-stack wall and a rockery wall?

Both are built without mortar. Dry-stack uses smaller, flatter stones stacked in courses. Rockery walls use large, heavy boulders (200-1,000+ lbs) placed by equipment. Rockery walls can be much taller and hold more weight. Dry-stack is more of a DIY technique for smaller garden walls.

Building a retaining wall? Harbor Soils delivers rockery stone, boulders, and drainage rock throughout Kitsap and Pierce Counties. Call us to estimate quantities for your project. Rockery stone delivery → | Drainage rock →